Retractor

ABSTRACT

A retractor ( 20 ) for a vehicle safety restraint for use in a rear vehicle seat comprising: seat belt webbing wound on a rotatable spool ( 2 ), and a vehicle sensor having an inertial sensor mass ( 5 ) supported in a housing and movable relative thereto when vehicle acceleration or deceleration exceeds a predetermined magnitude; a vehicle sensor pawl ( 7 ) arranged to be moved, in response to movement of the mass, from a position in which the spool is freely rotatable into a spool locking position; a seat back latching condition detector, adapted to be located in a latch for the rear seat back, means ( 10 ) connecting the latching condition detector to the vehicle sensing pawl, the connecting means being operable to move the pawl ( 7 ) into the spool locking position when a seat back deatched condition is detected.

DESCRIPTION

The present invention relates to a retractor for a vehicle safetyrestraint seat belt and particularly to a retractor for use in the rearpassenger seats of a vehicle and to a safety locking arrangementtherefor.

Retractors for rear seat belts are often mounted on the seat back restitself since space is at a premium in the rear passenger compartment.For the seat belt to be effective therefore the back rest must befastened securely to a fixed part of the vehicle. Normally this would bethe case. However in some vehicles, such-as so-called station-wagons orestate cars and so-called hatchback cars, the rear seat back rest can beunlatched from its fastened upright position and rotated into ahorizontal position to increase the luggage capacity of the vehicle. insome models the back rest is split and one part may remain upright toaccommodate a seated passenger while the other part is lowered to allowbulky luggage to overflow from the luggage compartment behind the seatback.

In both cases there is a danger that when the seat back rest is returnedto the upright position it may not be securely locked. In a crash, therear passenger will then not be safely restrained because the retractor,attached to the seat back, will move when the seat back moves under theinertial loading caused by the crash.

The rear seat retractor is constructed in a similar manner to a frontseat retractor and has both a web sensor and a vehicle sensor. The websensor locks the retractor against pay-out i, the belt webbing issuddenly jerked, as would happen if it were suddenly loaded by theinertia of the user in a crash. This is known technology. The vehiclesensor detects a sudden change of speed of the vehicle and locks theretractor, again in a manner known to those skilled in the art.

The vehicle sensor typically comprises an inertia sensitive ball restingfreely in a cup. A sudden deceleration of the vehicle causes the ball tokeep moving and to ride up the side of the cup. A pawl resting on theball is thus deflected upwards and this pawl activates a lockingmechanism to lock the retractor spool against rotation and thus againstfurther pay-out of webbing. The geometry of the ball type vehicle sensormeans that it will also be activated if the retractor is tilted. This isused in DE 29 27 159 and GB 2 249 339 as an inherent seat back tiltsensor. If the seat back is not upright then the vehicle sensor locksthe retractor against pay-out and it cannot be used.

However this known arrangement will not detect a rear seat back which isin the upright position but is not locked securely into the uprightposition. In this situation the retractor of the known arrangement canbe used to fasten a vehicle occupant who will be unaware that theretractor is free to move and thus that he is not safely restrained.

In GB 2 286 624 a sensor is located in the seat back latch itself. Whenthis detects that the latch is securely fastened it releases anadditional locking device on the retractor to allow the retractor to beused. This is an expensive system requiring an additional locking deviceto be fitted to the retractor.

The present invention aims to provide an improved safety lockingarrangement for a retractor in a rear seat.

According to the present invention there is provided a retractor for avehicle safety restraint for use in a rear vehicle seat, the retractorcomprising:

seat belt webbing wound on a rotatable spool, and a vehicle sensorhaving

an inertial sensor mass supported in a housing and movable relativethereto when vehicle acceleration or deceleration exceeds apredetermined magnitude,

a vehicle sensor pawl arranged to be moved, in response to movement ofthe mass, from a position in which the spool is freely rotatable into aspool locking position,

a seat back latching condition detector, adapted to be located in alatch for the rear seat back,

means connecting the latching condition detector to the vehicle sensingpawl, the connecting means being operable to move the pawl into thespool locking position when a seat back de-latched condition isdetected.

According to a preferred embodiment of the present invention theconnecting means comprises a bowden cable which is moved, preferablypulled, when the latch is in a disengaged state. The bowden cable isconnected to a piston in the retractor which is spring biased to aposition in which it has no effect on the retractor. However when theseat back latch is disengaged, the bowden cable pulls the piston againstthe spring bias The piston operates a lever which rotates the vehiclesensor pawl into the spool locking position in which the spool is lockedagainst belt webbing pay-out. Thus the retractor cannot be used by anoccupant who is thus alerted to the insecure state of the seat back.

Once the seat back latch is properly engaged, the pull on the bowdencable is released and the piston in the retractor returns to the normalposition. The retractor is free to pay-out, subject to inertialinfluence on the vehicle sensor—such as in a crash

A retractor according to the invention is advantageous compared to knownsuch retractors. Since the vehicle sensor pawl is used for locking thespool against belt webbing payout, a minimum number of extra componentsis reouired with attendant cost savings and increased reliability. Inaddition, in the safety locking condition, the retractor is fully andpositively locked in a load bearing manner. The additional retractorlocking devices used in known systems comprise much weaker, simple pawlengagement systems which are less reliable and are not capable ofwithstanding high loads.

For a better understanding of the present invention and to show how thesame may be carried into effect, reference will now be made to theaccompanying drawings in which:

FIG. 1 is a -cross-sectional view of a retractor according to thepresent invention illustrating the condition with the seat properlylatched and the vehicle sensor inactivated;

FIG. 2 is a cross-sectional view of the retractor of FIG. 1 with theseat properly latched and the vehicle sensor activated (crashcondition);

FIG. 3 is a cross-sectional view of the retractor of FIG. 1 with theseat not properly latched.

FIG. 4 is a schematic side view of a vehicle seat incorporating aretractor according to the present invention.

FIG. 5 is a side cross-sectional view of belt webbing forming part ofFIG. 4.

FIG. 6 is a front view of belt webbing forming part of FIG. 4.

In the Figures a retractor 20 is shown in cross-section, and comprises aframe 1, a spool 2 on which belt webbing is wound, and a lock-cup 3which engages and locks the spool against rotation under predeterminedconditions.

A vehicle sensor 4 comprises a sensor ball 5 resting in a shallow cup 6.A sensor pawl 7 is hinged to the vehicle sensor housing at pivot point 8and rests on top of the pawl 7. Movement of the ball 5 lifts the pawl 7by rotation and pawl 7 in turn lifts a pilot arm 9 which locks the spool2 with the lock-cup 3 preventing further rotation of the spool andpay-out of webbing.

A bowden cable 10 is connected to a seat latch (not shown). When theseat is fully latched the cable is in a protracted condition. When theseat is unlatched, the cable lo is pulled in direction A. The connectioncan be made in a variety of ways which will be evident to a personskilled in the art.

The cable 10 is attached to a piston 11 mounted in a piston housing 12.The piston il is biased by spring 13 to an upper position (as shown inFIG. 1). A leaf spring 14 is fixed to and bent over the top of thepiston 11, with one arm extending in the direction of the vehicle sensorpawl 7.

FIG. 1 shows the condition when the seat back latch is properly engaged.The bowden cable 10 is in the protracted position, the piston 11 is inthe upper position and leaf spring 14 is well clear of the vehiclesensor pawl 7. Thus the spool is free to rotate and the vehicle sensorwill operate as normal if a crash is detected. In FIG. 1 the vehiclesensor ball 5 is shown sited centrally of the cup 6, as for a non-crashcondition.

FIG. 2 illustrates the condition when the seat back latch is properlylatched but a crash condition has occurred. As in FIG. 1 the cable 10 isprotracted, the piston 11 is in the upper position and the leaf spring14 is clear of the vehicle sensor pawl 7. However the vehicle sensorball 5 has been moved by crash induced inertia to an off-centreposition. Thus the pawl 7 has rotated upwardly, lifting pilot arm 9 andengaging the lock-cup 3 with the spool 2. Thus the spool is lockedagainst further belt webbing pay-out and the occupant is securelyrestrained.

In FIG. 3, the seat back is not properly latched. The bowden cable 10 isretracted in the direction of arrow A and piston ll is pulled downwardlyagainst the bias of spring 13. The outwardly extending arm of the leafspring 14 contacts the rearwardly extending arm of the sensor pawl 7 androtates the pawl 7 into engagement with pilot arm 9. Thus the lock-cupengages with the spool and the spool is locked against belt webbingpay-out. Thus the retractor cannot be used and the vehicle occupant isalerted to the insecure latching condition of the seat back. In thiscondition the vehicle sensor is inoperative.

The leaf spring 14 rotates the sensor yawl 7 during the first part ofthe stroke. Any further pull on the cable 10 and thus on piston 11 willbe absorbed by deformation of the spring 14.

It will be understood by anyone skilled in the art that the arrangementcould operate in the opposite manner, i.e. that the signal from the seatlatch could influence the spool locking mechanism by a pushing motionrather than a pulling action.

FIG. 4 schematically illustrates the vehicle seat incorporating theretractor 20 of FIGS. 1 to 3.

The vehicle seat 21 comprises a back 22 to which retractor 20 is fixedas shown. A head rest 23 is mounted to the top of the back 22. The back22 pivots about point D into a variety of meeting and forward positionsone of which is indicated by broken line 22′ with the retractor stillattached as shown at 20′.

A seat squab 24 pivots about point C into an upright position as shownby-broken line 24′.

Seat belt webbing 25 is arranged in the typical three point arrangementfor safety restraints. One end of webbing 25 is fixed to the vehiclechassis at B, and the webbing passes up the front of the seat back 22over the top, between the back 22 and the headrest 23, and is wound ontothe retractor 20 other end is wound onto retractor 20.

A tongue 26 for fastening the belt in a buckle (not shown) is attachedto the webbing 25.

When the seat back 22 is rotated to the lowered position (dotted lines22′) it can happen that the effective distance from the top A, A′ of theseat to the fixing part B of the belt, is shortened. Thus AB is longerthan A′ B and the belt webbing 250 becomes loose and the extra is woundonto the retractor 20. In this case, the seat back 22 is prevented frombeing returned to its upright position by the shorter length of the freeFelt webbing 25′, since the retractor 20′ is located against webbingpayout.

This problem can be alleviated by the addition of a plastic mouldedbutton 27, or the webbing as shown in FIGS. 5 and 6. This button 27cooperates with a slot 28 in the webbing guide 29 on the retractor 20,to prevent take up of the belt beyond the level at which the belt isPresented to the occupant in normal use. Thus further retraction of thebelt is impossible beyond this level and there will always be sufficientwebbing to allow return of the seat back to an upright position.

FIG. 6 illustrates the webbing and button in more detail. The webbing 25fits through a slot 30 on a tongue 31 so as to be freely slidable toachieve the optimum position on the webbing when fastened. This positionof course depends on the geometry of the vehicle seat and the physicalshape and size of the occupant. The tongue slot 30 thus has a widercentral area 32 to allow the tongue to slide over button 27. FIG. 6 alsoshows two additional buttons 33 offset from the centre of the webbing.These buttons 33 stop the tongue falling down for example below thelevel of the seat squab, when the belt is not being worn.

What is claimed is:
 1. A retractor for a vehicle safety restraint foruse in a rear vehicle seat, the retractor comprising; seat belt webbingwound on a rotatable spool, and a vehicle sensor having: an inertialsensor mass supported in a housing and movable relative thereto whenvehicle acceleration or deceleration exceeds a predetermined magnitude,a vehicle sensor pawl arranged to be moved, in response to movement ofthe mass, from a position in which the spool is freely rotatable into aspool locking position, a seat back latching condition detector, adaptedto be located in a latch for the rear vehicle seat, means connecting thelatching condition detector to the vehicle sensor pawl, the connectingmeans being operable to move the pawl into the spool locking positionwhen a seat back de-latched condition is detected; wherein theconnecting means comprises a bowden cable connected to a piston in theretractor which is spring biased to a position in which it has no effecton the retractors but is arranged so that when the seat back latchingcondition detector detects a seat disengaged condition, then the bowdencable pulls the piston against the spring bias.
 2. A retractor accordingto claim 1 comprising a lever operatively connecting the piston to thevehicle sensor pawl and operable to move it into the spool lockingposition in which the spool is locked against belt webbing pay-out.